| Diesel engines are used as the main power in commercial vehicles,because of its strong power,low fuel consumption advantages are more prominent.However,the impact of exhaust pollutants on the atmospheric environment has been the focus of the international community.China has been using SCR technology to reduce the nitrogen oxide in diesel engine emissions since the stage of China’s IV emission standard.The China VI emission stage set higher requirements for the control of exhaust pollutants and higher requirements for NOx conversion efficiency.Therefore,China VI stage SCR system catalyst used copper-based molecular sieve catalyst.Compared with the vanadium-based SCR catalysts used in China V,there are great differences in the performance of the catalyst itself,the dosing control strategy is completely different.In this paper,the characteristics of catalyst,the design and development of injection control strategy and the verification of emission test are studied.Through the study of the characteristics of the copper-based molecular sieve catalyst,according to the structure and working principle of the SCR system,the SCR system control software first needs to filter the signals of the sensors of the SCR system to ensure the authenticity of the signals.At the same time,considering the influence of diesel engine condition on exhaust,the delay treatment of injection control is carried out to ensure the following of NOx conversion.Since temperature is a key factor affecting the conversion efficiency of copper-based molecular sieve catalysts to NOx.Based on the principle of energy conservation,the temperature model of the carrier of the SCR system is established.The temperature of the carrier core will be accurately calculated.Then,according to the NOx emission requirements of emission regulations,combined with the characteristics of the copper-based molecular sieve catalyst,open-loop and closed-loop injection control strategies were designed and developed to ensure that the diesel engine can meet the requirements of emission regulations during the emission warranty period required.According to the emission test requirements of the China VI stage,the requirements and methods of engine bench and vehicle emission test cycle are analyzed,and the WHTC、WHSC and WNTE engine bench emission cycle test and vehicle PEMS emission test are carried out.All the test results meet the emission limit and verify the reliability of injection control strategy. |
